Some research, however, suggests that several genetic variants involved in carotenoid metabolism could influence lycopene bioavailability. A 2020 A placebo-controlled, randomized, double-blind, crossover trial on postmenopausal women examined how pure watermelon juice affected blood levels of lycopene, fats, and antioxidant capacity, as well as the influence of genes of lycopene metabolism and bioavailability.
The researchers assessed the effects of 100% watermelon juice on mechanistic and clinical outcomes related to vascular function. The study participants were given low-lycopene diets for a 1-week period and throughout the study. They consumed a daily dose of 14.4 ± 0.34 mg of lycopene. Study periods of 4 weeks were separated by 2-week washout periods. Saliva was collected for genetic analysis of single nucleotide polymorphisms, or genetic variation, and fasting blood samples were taken pre- and post-study arms.
The results showed that, though the watermelon juice didn’t result in significant changes in serum lipids or antioxidant capacity, lycopene blood levels rose significantly as a result of the watermelon treatment. Interestingly, results were also notably different across the individuals tested. People with the rs6564851 genetic variant in the beta-carotene 15,15’-oxygenase-1 gene were associated with changes in lycopene, and TT homozygotes exhibited a significantly greater increase. This occurred while efforts were made to ensure that the variability wasn’t attributable to intervention compliance or background diet.
The researchers concluded that personalized nutrition recommendations based on genotyping could help overcome individual responses to lycopene interventions, though a larger trial is needed to fully help confirm the results seen here.